1. Field of the Invention
The present invention relates to a reinforcing structure for automotive vehicles applied to structural members such as a cross car beam in the instrument panel of the vehicle.
2. Description of the Related Art
In the prior art, as shown in FIG. 1, a cross car beam (CCB) 1 having side brackets 2 at the ends thereof is suspended between left and right front pillars as a structural member, at the back of the instrument panel, in the vehicle. On this cross car beam 1, a steering shaft 3 having a steering wheel 31 is fixed by a steering shaft support 4.
This conventional cross car beam 1, as shown in FIG. 15, is constituted of a large-diameter round pipe and supported by braces 5 erected on the vehicle floor. Taking the convenience for assembling on the vehicle into consideration, the cross car beam 1 has brackets (not shown) connected with ends of the braces 5 by bolts or the like. In this connecting method, however, a sufficient rigidity against twisting cannot be secured and, therefore, steering shaft vibration cannot be prevented.
In order to obviate the problem described above, an improved conventional method of connecting the cross car beam 1 and the braces 5 has been proposed in Japanese Unexamined Patent Publication No. 8-183478.
In this improved connecting method, vertical through holes are formed in the pipe of the cross car beam 1, and with the forward end of each brace 5 inserted in the corresponding one of the through holes, the braces and the pipe are fixedly welded to each other.
With the conventional cross car beam structure described above, however, a thick round pipe having a large section diameter is required to secure the strength and, therefore, the problem is posed of a low space utilization rate and a larger weight. An alternative structure, which has been proposed to secure the strength by increasing the diameter of only the part nearer to the driver's seat, requires the additional steps of increasing the pipe diameter or welding a small-diameter pipe and a large-diameter pipe to each other at a higher cost. Another problem is that the diameter of the round pipe portion nearer to the driver's seat is increased and this lowers the freedom for effective space utilization.